Reflex klystron



11, 1959 F. SALISBURY ET AL ,5

' REFLEX KLYSTRON Filed Dec. 1956 2 sheets-sneer 1 Fig.3

INVENTOR. Frederick L. Salisbury y 8 Wayne 6. Abrqham 1 Affdrr ey Aug. 11, 959 F. L. SALISBURY ET AL 2,899,599

- REFLEX KLYSTRON Filed Dec. 13, 1956 2 Sheets-Sheet 2 INVENTQR. F g 4 Frederick L.Sa/1sbury y Wa ne GAbraham M, M

Attorney United States Patent REFLEX KLYSTRON Frederick L. Salisbury, Los Altos, and Wayne G. Abraham, Palo Alto, Calif, assignors to Varian Associates, San Carlos, Calif., a corporation of California Application December 13, 1956, Serial No. 628,152

18 Claims. (Cl. SIS- 5.21)

erators of very high radio frequencies. The electronic systemsin present day use and planned for the future require increasingly higher and higher radio frequency signal sources and, in accordance with well-known reflex klystron theory, as the frequency of operation increases, the physical size of the reflex klystron producing such frequencies decreases. However, even though the size of the reflex klystron is decreasing, the requirement on ruggedness of the klystron becomes more and more acute due to the end use of such high frequency klystrons. For example, high frequency sources in the K-band region are required for systems subject to rough treatment yet, because of the abuse to which the system is to be subjected, the radio frequency source producing such high frequency must be extremely rugged." The dual requirements of small size accompanied by rugged construction are not ordinarily compatible and are not easily met in practice. In addition to the requirements of high frequency and exceptional ruggedness, the klystron must also be capable of being tuned over an appreciable band of frequencies rapidly and with ease, yet must be extremely stable against undesired drift in frequencies.

The present applicants have succeeded in constructing a reflex klystron of the tunable external cavity type whichsuccessfully meets these necessary requirements. This particular embodiment of the invention operates in the band of frequencies of from about 34 kilomegacycles to between 35 and 36 kilomegacycles.

It is, therefore, the object of the present invention to provide a very small, light weight reflex klystron for operation in high frequency regions which is extremely rugged in construction to withstand severe abuse.

One feature of the present invention is the provision of a novel reflex klystron constructed from a bare mini-- mum of separate components assembled in a rugged unitary device capable of meeting the object of the present invention.

Another feature of the present invention is the provision of a novel reflex klystron in which the main portion of the klystron consists of a unitary body of metal in which a cathode, internal cavity resonator, and reflector electrode are mounted and a second body of metal securely aflixed to the main body which serves the combined functions of external cavity resonator, output waveguide, mounting fiange, and tuner mount.

Still another feature of the present invention is the provision of a novel reflex klystron device of the above featured type wherein the second body of metal is formed from a larger body having a threaded bore therein, the larger body being split longitudinally through said bore and having a tuning screw threaded therethrough so that the two parts of the larger body may be heavily spring loaded to securely aflix the tuning screw therein.

' ice Still another feature of the present invention is the provision of a novel electron tube apparatus employing a first cavity resonator interacting with an electron beam within the apparatus and a second cavity resonator heavily coupled through an iris opening to said first cavity resonator, said second cavity resonator having an output iris member provided in one side thereof for coupling electromagnetic energy from said second cavity resonator to a load, and a conducting member protruding into the vicinity of the iris opening in said latter member for both controlling the degree of electromagnetic coupling between the load and the discharge device and for suppressing one of the undesired modes of operation of the device.

These and other features and advantages of the present invention will become more apparent from a perusal of the following specification taken in connection with the accompanying drawings wherein,

Figs. 1, 2 and 3 are front, top and side elevation views, respectively, of the novel reflex klystron embodying the j present invention,

Fig. 4 is a longitudinal cross section view of the novel klystron taken along section lines 44 in Fig. 1,

Fig. 5 is a transverse cross section view of the klystron taken along section line 5-5 in Fig. 4, and

Fig. 6 is a plan view of a portion of another reflex klystron embodying the present invention.

Referring now to the drawings this preferred embodiment of the invention comprises a main body 1 1 which is made from a unitary block of metal, this main body consisting of a substantially rectangular block portion 12 and an enlarged cylindrical end portion 13 joined together by areduced diameter cylindrical connecting portion 14, the rectangular block portion 12 having a cylindrical extension thereon forming a reduced diameter end 15'on the main body 11. This main body 11 has a multidiameter bore extending longitudinally therethrough, the axis of the multidiameter bore coinciding with the axes of the cylindrical body portions 13, 14 and 15.

Fixedly secured within the enlarged bore in the large cylindrical end portion 13 of the main body is a cathode mounting structure comprising an annular mounting ring member 16 into which is securely aflixed a ceramic insulating disc 17. A cathode structure is fixedly secured as by brazing on the ceramic disc 17 and comprises a cathode mounting stem 18 having a cathode button 19 mounted on the inner end thereof and having a filament 21 extending within the stem. Also mounted on the ceramic disc 17 by certain ones of a number of spaced wire supports 22 and encircling the stem 18 and button 19 is a hollow cylindrical focusing member 23 for properly focusing the electrons which are emitted from the cathode button into a desired electron beam. The ends of the filament protruding from the bottom of the stem 18 are electrically connected to one of the support wires 22. An open ended cup-shaped member 24 is vacuumsealed within the bore of the body portion 13, the lower open end of the cup 24 being sealed by a vacuum sealmaterial 25 such. as glass. The electrical leads leading to a getter 26, the filament 21 and the body 11 extend out from the klystron through this sealing glass 25 and are embedded in an insulating silicon gum polymer cap 27 encasing the cathode end of the klystron.

Fixedly secured as by brazing within the smallest diameter portion of the bore which lies within the rectangular block portion 12 of the body is a reentrant tube member 28 which has a resonator grid 29 mounted onthe inner end thereof. Accelerating grid 31 is brazed on the body within the bore and adjacent this re-entrant tube 28. Also fixedly secured as by brazing within this section of the body is a hollow cylindrical resonator grid mounting member or header 32 on which is fixedly secured as by brazing another resonator grid 33 which serves to cooperate with the first resonator grid 29 in' stem cap 35, this cap being in turn fixedly mounted on an annular insulating member 36 as of ceramic. This member 36 is vacuum-sealed to an annular reflector mounting member 37 which in turn is fixedly secured within the reflector end 15 of the klystron. The stem is connected to an external lead which is embedded in an insulating end cap 37.

, Another bore extends into the rectangular block portion 12 of the main body from one side and has a pinch-off tube 38 brazed therein through which this klystron is evacuated, the tube 38 being pinched oil and sealed closed after evacuation and then being covered and protected from damage by a silicon gum polymer cap 39.

A substantially rectangular-shaped, two step opening 41 is located in another side of the rectangular block portion 12 of the body and extends into the internal cavity resonator formed by the headers 28, 32 and the resonator grids 29, 33. Vacuum-sealed within this rectangular opening on the step thereof is a wave energy permeable material 42 such as mica.

A waveguide flange member 43 is fixedly secured as by screws 40 on the main body 11. This flange member is formed from a unitary rectangular-shaped body of metal and serves the combined functions of external cavity resonator, output waveguide, mounting flange, and tuner mount. This waveguide flange member 43 has a twodimension rectangular opening therethrough, the enlarged section 44 of this rectangular opening being adapted to coincide with the rectangular opening 41 in the main body 11 to form the external cavity resonator of this external-internal cavity resonator klystron. The reduced dimension section 45 of this rectangular opening forms an output waveguide leading from the external cavity resonator to the external load. Fixedly secured within the rectangular opening in this waveguide member at the junction of the two sections 44, 45 is an iris plate mem ber 46 having an opening 46' therein forming the iris coupling window between the external cavity resonator and the external load. A small screw 47 is secured in the flange and extends into the external cavity resonator opening to serve as a mode suppressor of the undesired x mode. Another screw member 48 which, for example, may be brass is carried in the flange member 43 and pr@ trudes into the opening 45 adjacent to the iris plate 46 and serves as an iris loading member for optimum electromagnetic coupling between the external cavity resonator and the output waveguide and also serves as a mode suppressor which overcouples to the 2 mode.

Also located in the waveguide flange member 43 is an elongated tuning screw member 49 having a screwdriver slot in its outer end, a central threaded portion 51 and a reduced diameter, rod-like end portion 52 adapted to ex-- tend within the external cavity resonator to form a capacitive tuning post therein. The threads on said tuning screw member cooperate with internal threads on a bore extending vertically within the waveguide flange for threading the capacitive tuning post into the external cavity resonator.

As stated above, the waveguide flange member 43 is formed from a unitary block of metal but, after the waveguide flange had been drilled and tapped to produce the tuning screw threads, the block. was split longitudinally v tuning screw bore so that essenthrough the axis of the tially two halves 53 and 54 were formed in the upper portion of the member. A strong spring clip 55 is used to secure the two halves 53, 54 of the upper flange portion together and grip the tuning screw 49 therebetween so that shaking or vibration of the klystron will not cause the tuning screw to move within the threaded bore, the tuning movement resulting only from a rotational force being applied by a screw driver or the like to the upper end of the tuning screw. Screws 50 could be used to clamp the two halves 53, 54 together instead of the spring clip 55, if desired, as shown in Fig. 6. A plurality of choke joints 56 are provided in the bore through which the tuner rod end 52 extends into the external cavity resonator for preventing-the escape of radio frequency energy through this opening.

One embodiment of the present invention as constructed tuned a band of frequencies from 34.0 to 35.6 kilomegacycles in about 1 /2 turns of the tuning screw 49. The spring loaded tuning screw 49 insured a smooth tuning action and permitted easy setting to a given frequency. The particular klystron device under discussion operated at a low beam voltage .of 400 volts, average tubes of this type putting out about 20 milliwatts of power with about 70 to 80 megacycles of bandwidth. Some tubes exhibited as much as 40 milliwatts of power and 100 megacycles of bandwidth. The

reflector voltage mode is the one usually used although oscillations have been observed in other modes such as the full wave cavity mode. Although in the particular embodiments shown in the drawings the and the plus IH wave cavity mode are suppressed, the klystron device may be operated in such modes by removing the suppressiml, if desired.

Since many modifications in and variations from the described apparatus may be made without departing from the spirit of the invention, the foregoing embodiment of the invention is to be considered as exemplary and not in a limiting sense.

What is claimed is;

1. An electron discharge device comprising a main body, means adapted to produce an electron beam within the body, said body having a cavity resonator formed within the same in the beam path for electromagnetic interaction with the electron beam, said body having an opening in the side thereof extending into the cavity resonator, a wave permeable vacuum seal in said opening, a waveguide flange fixedly secured on said first body, and adapted for mounting the device on an output load, said waveguide flange having an aperture therethrough, one end of which coincides with the opening in said first body, one portion of said aperture in said waveguide flange forming an external cavity resonator heavily coupled through said vacuum seal to said first cavity resonator, and a second portion of said aperture being. reduced in cross-sectional area, and serving as an output waveguide coupled to said external cavity resonator, and a tuning screw mounted on said waveguide flange and extending within said external cavity resonator opening for tuning the electron discharge device.

2. Anelectron discharge device as claimedin claim 1 including an iris plate positioned in said aperture at the junction of said two portions of the aperture; said iris plate having an iris opening therein for couphng the external cavity resonator portion of the aperture to the output waveguide portion of the aperture.

3. An electron discharge device as claimed in claim 1 wherein said main body cavity resonator and said Waveguide flange cavity resonator cooperate in operation to form a single cavity resonator operating in full wave mode.

I 4. An electron discharge device as claimed in claim 3 wherein said waveguide flange is provided with means for suppressing unwanted 2 A and 2 A modes.

5. An electron discharge device as claimed in claim 4 wherein said suppressing means comprises a plurality of screws projecting into said waveguide flange opening.

6. An electron discharge device comprising a main body, means adapted to produce an electron beam in the body, said body having a first cavity resonator formed therein in the beam path for electromagnetic interaction with the electron beam, said body having an opening in the side thereof extending into the cavity resonator, a wave permeable vacuum seal in said opening, a waveguide flange adapted for mounting the device on an external load circuit and having an aperture therein which coincides with the opening in said first body, said waveguide flange being mounted on said first body, the aperture in said waveguide flange serving to form an external cavity resonator heavily coupled through said vacuum seal to said first cavity resonator, one side portion of said waveguide flange being made up in two halves, said two halves having threaded surfaces thereon whereby said two halves, when mated, form a threaded bore extending between the two halves, a threaded tuning screw extending through said threaded bore and into the external cavity resonator opening in said waveguide flange for tuning the external cavity resonator, and means for clamping the said two halves together so as to firmly grip the tuning screw therebetween.

7. Apparatus as claimed in claim 6 wherein said means for clamping said two halves together comprises a flexible spring member.

8. Apparatus as claimed in claim 6 wherein said means for clamping said two halves together comprises screw means.

9. Apparatus as claimed in claim 6 including radio frequency choke means secured in the bore in said waveguide flange through which said tuning screw extends, said choke means preventing the escape of RF. energy from said external cavity resonator along said tuning screw.

10. An electron discharge device comprising a main body, means adapted to produce an electron beam in the body, said body having a cavity resonator formed therein in the beam path for electromagnetic interaction with the electron beam, said body having an opening in the side thereof extending into the cavity resonator, a wave permeable vacuum seal in said opening, a waveguide flange mounted on said body and having an aperture therein which coincides with the opening in said body, one portion of said aperture in said waveguide flange member forming an external cavity resonator heavily coupled through said vacuum seal to said first cavity resonator, another portion of the aperture in said waveguide flange serving as an output waveguide coupled to said external cavity resonator, an iris plate positioned in the aperture in said waveguide flange at the junction of said two portions, said iris plate having an im opening therein for coupling the external cavity resonator portion of said aperture to the output waveguide portion of said aperture, one side portion of said waveguide flange being made up in two halves, said two halves having threaded surfaces thereon whereby said two halves, when mated, form a threaded bore extending between the two halves, a threaded tuning screw extending through said threaded bore and into the external cavity resonator in said waveguide flange for tuning the external cavity resonator, and means for clamping the said two halves together so as to firmly grip the tuning screw therebetween.

11. Apparatus as claimed in claim 10 wherein said means for clamping said two halves together comprises a flexible spring member.

12. Apparatus as claimed in claim 10 wherein said means for clamping said two halves together comprises screw means.

13. An electron discharge device comprising a main body, means adapted to produce an electron beam in the body, said body having a first cavity resonator formed therein in the beam path for electromagnetic interaction with the electron beam, said body having an opening in the side thereof extending into the cavity resonator, a wave permeable vacuum seal in said opening, a waveguide flange adapted for mounting on an output load circuit and having an aperture therein which coincides with the opening in said first body, said waveguide flange being mounted on said first body, one portion of the apelture in said waveguide flange serving to form an external cavity resonator heavily coupled through said vacuum seal to said first cavity resonator, another portion of the aperture in said waveguide flange serving to form an output waveguide coupled to said external cavity resonator through an iris opening, a tuning member mounted on said waveguide flange and extending within said external cavity resonator for tuning the electron discharge device, and a conducting member mounted on said waveguide flange and protruding into the Vicinity of the iris opening between the external cavity resonator and the output waveguide for controlling the degree of electromagnetic coupling between an output load and the electron discharge device and for suppressing one of the undesired modes of operation of the electron discharge device.

14. An electron discharge device as claimed in claim 13 wherein said tuning means comprises a screw which is threaded through said waveguide flange into said external cavity resonator.

15. An electron discharge device as claimed in claim 14 wherein said waveguide flange is split through the threaded bore in which said tuning screw is located, and means for clamping the split section of the waveguide flange to the waveguide flange so as to firmly grip the tuning screw therein.

16. An electron discharge device comprising a main body, means adapted to produce an electron beam in the body, said body having a first cavity resonator formed therein in the beam path for electromagnetic interaction with the electron beam, said body having an opening in the side thereof extending into the cavity resonator, a wave permeable vacuum seal in said opening, a waveguide flange having an aperture therein which coincides with the opening in said body, said waveguide flange being mounted on said first body and serving to couple the electron discharge device to an output load having a matching flange, the aperture in said waveguide flange serving to form an external cavity resonator heavily coupled through said vacuum seal to said first cavity resonator, and a tuning member mounted on said waveguide flange and extending within said external cavity resonator for tuning the electron discharge device.

17. An electron discharge device as claimed in claim 16 wherein said tuning means comprises a screw which is, thneaded through. said waveguide flange into. said ex temal. cavity resonator.

- 1:8. .An: electron discharge device,v as claimed in claim 1-7 wherein-said waveguide flange issplit through the threaded herein which saidtuning screw is located, and

means for clamping the split sectionof the waveguide flange tothe waveguide flange so as to firmly grip the tuning screw'therein.

References Cited in the file of this patent UNITED STATES PATENTS 159,491 Ban'owclough Feb. 9, 1 875 FOREIGN PATENTS France Sept. 14, 1955' 

